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COMPARATIVE ANALYSIS OF COMMUNICATION ARCHITECTURES AND 
TECHNOLOGIES FOR SMART GRID DISTRIBUTION NETWORK 

by 

Monther A. Hammoudeh 

B.S.E.E., Virginia Polytechnic Institute and State University, 1995 



A thesis submitted to the 

University of Colorado Denver 

in partial fulfillment 

of the requirements for the degree of 

Masters of Science Electrical Engineering 

Electrical Engineering 

2012 



This thesis for the Masters of Science Electrical Engineering 

degree by 

Monther A. Hammoudeh 

has been approved 

by 



Fernando Mancilla-David 



Titsa Papantoni 



Dan Connors 



Date: May 4, 2012 



Hammoudeh, Monther A. (M.S., Electrical Engineering) 

Comparative Analysis of Communication Architectures and Technologies for Smart 
Grid Distribution Network 

Thesis directed by Assistant Professor Fernando Mancilla-David 



ABSTRACT 

A critical piece of the Smart Grid infrastructure is the communications 
network for data gathering, control and supervision capabilities that extend to the 
customer demarcation point. Over several decades, the electric utilities built a robust 
communications networks connecting electric grid subsystems except for the "last 
mile" connecting to the end user premise. A primary goal of Smart Grid (SG) is to 
expand the communications network throughout the Distribution Network (DN) thus 
enabling a holistic management and control of electric grid from generation to 
consumption. In order for the Smart Grid goals to be realized, two-way 
communications network must extend to the Distribution Network allowing two-way 
data flow e.g., real-time energy pricing and real-time demand data back to the 
Utilities and Operators. This thesis presents five communications architectures and 
viable technologies for deployment within the Distribution Network of the Smart 
Grid. Then apply selected metrics to these architectures and technologies 
combinations and select top five scoring combinations. 



This abstract accurately represents the content of the candidate's thesis. I recommend 
its publication. 

Approved: Fernando Mancilla-David 



DEDICATION 

All thanks and praise is due to Allah for his blessing and guidance. 
I dedicate this thesis to my loving parents, especially my father (the late Professor 
Abed El-Rahman Hammoudeh) who gave me the appreciation of education and 
taught me the value of perseverance and resolve. I also dedicate this thesis to my 
wife, Suhad, and my daughters (Mona, Hoda and Ayah) for their understanding and 
sacrifice while I was completing this thesis. I would like to thank all my family and 
friends who supported me to successfully finish this work. 



ACKNOWLEDGMENT 

My thanks to my advisor, Dr. Fernando Mancilla-David, for his contribution and 
support of my research. I also wish to thank all the members of my thesis committee 
for their valuable participation and insights. 



CONTENTS 

Figures x 

Tables ix 



Chapter 

1 . Introduction 1 

1.1 Scope of This Study 2 

1.2 Organization of Thesis 4 

2. What is Smart Grid? 5 

2. 1 Recent American Laws Driving Smart Grid Deployment 6 

2.2 Smart Grid Functions and Goals 7 

2.3 Smart Grid Benefits 9 

3. Data Collection in The Distribution Network 1 1 

3.1 Consumer Energy Usage Data 12 

3.2 Device Status Data and Control 12 

4. Communications for The Distribution Network 15 

4. 1 The Need for Communications 15 

4.2 Communications Requirements 16 

4.3 Are Smart Grid Standards Required? 19 

4.4 Emerging Smart Grid Standards 19 

5. Communications Architectures 21 

5.1 Direct Connect Architecture 22 

5.2 Local Access Aggregators Architecture 23 

5.3 Interconnected Local Access Aggregators Architecture 26 

5.4 Mesh Architecture 27 



vn 



5.5 The Internet Cloud Architecture 28 

6. Technology Options 3 1 

6.1 Wireline Technology Options 31 

6.2 Wireless Technologies 35 

7. Analysis Methodology and Approach 39 

7.1 Metrics 39 

7.2 Analysis Methodology 43 

7.3 Summary of Results 44 

7.4 Conclusion 5 1 

Bibliography 52 



vin 



FIGURES 

Figure 

5.1 A view of the Utility Information Systems 22 

5.2 Direct Connect Architecture 23 

5.3 Overview of AMI Network with NAN 24 

5.4 Local Access Aggregator Architecture 25 

5.5 Interconnected Local Access Aggregators Architecture 26 

5.6 Mesh Architecture 27 

5.7 The Internet Cloud Architecture 30 



IX 



TABLES 

Table 

2.1 The Smart Grid vs. The Existing Grid 8 

2.2 Cost of One-hour Service Outage 9 

3.1 Sample Data Requirements 13 

4.1 Communications From Customer's Gateway and Requirements 17 

4.2 Communications To Customer's Gateway and Requirements 18 

6.1 Qualitative Characteristics of Wireline Communication Media Types 35 

6.2 Qualitative Characteristics of Wireless Communication Technologies 38 

7.1 Metrics Guidelines 43 

7.2 Summary of Architecture 1 Metrics 45 

7.3 Summary of Architecture 2 Metrics 46 

7.4 Summary of Architecture 3 Metrics 47 

7.5 Summary of Architecture 4 Metrics 48 

7.6 Summary of Architecture 5 Metrics 49 

7.7 Top Five Architecture and Technology Combinations 50 



1. Introduction 

Over several decades, the electric utilities built a robust communications 
networks connecting electric grid subsystems except for the Distribution Network 
(DN) feeding the end customer premise. A primary goal of Smart Grid is to expand 
the communications network to the consumption segment thus enabling a holistic 
management and control of electric grid from generation to consumption. 

With the recent emphasis on deployments of Smart Grid within the United 
States of America and the passing of EISA (Energy Independent and Security Act of 
2007) into law [1], the race is on to begin deployment of Smart Grid. Under Title 
XIII of EISA 2007, the U.S. Department of Energy (DoE) established a Federal 
Smart Grid Task Force. In its Grid 2030 vision, the objectives are to construct the 
21 st century electric system to provide abundant, affordable, clean efficient and 
reliable electric power anytime, anywhere [2]. A key enabler of Smart Grid 
deployment is the communications network that interconnects the numerous devices, 
users' smart meters and the electric grid subsystems. The first step of designing a 
robust communications network is establishing an architecture that outlines data flow 
among various parts of the system. 

The North American power grids are made up of almost 3,500 utility 
organizations [3]. The basic principle of supplies and demand must be at equilibrium 
all times. Extensive communications networks that span hundreds of thousands of 



1 



miles enable electricity grid operators to manage the demand and keep this supply 
demand equation balanced. However, the existing communications architecture is 
several decades old and has not benefited from recent technology advances. 
Additionally, the existing communications network primary function is to connect 
electrical substation with operators control centers leaving the distribution subsystem 
lacking adequate situational awareness [3]. To remedy the current limitations of the 
electrical grid, the U.S. Congress passed the EISA law in 2007 establishing goals for 
modernizing the electrical grid. 

1.1 Scope of This Study 

A critical piece of the Smart Grid infrastructure is the communications 
network that will extend the control and supervision capabilities to the end users. As 
described in [4], the Smart Grid communications network can be divided into four 
distinct segments: 

• Core or metro segment - connects substations to the utilities' headquarters. 

• Backhaul segment - connects data aggregators to substation/distribution 
automation at broadband speeds 

• Neighborhood Area Network (NAN) or last-mile - connects the customer's 
smart meter or gateway to the data aggregators, and 



• Home Area Network (HAN) - this is the customer's home or building 

automation. 

The generation subsystem enjoys full automation while transmission and 
substation have very high levels of automation, but the distribution network has poor 
automation level [5], Additionally, the transmission-system level, area control 
centers and regional reliability coordination centers have been exchanging system 
status information. The communication links between these systems now cover the 
country with increasing exchange of information among electric utility companies 
[6]. 

The distribution segment of the electric grid is the least communicated with 
and least controlled segment of all the electric grid segments. The Distribution 
Automation (DA) is primarily led by substation automation with feeder equipment 
automation still lagging [6]. Because feeder automation lags other automation efforts 
widely, this area should be addressed directly in future work [6]. As discussed in [7], 
the Distribution Network remains outside the utility companies' real-time control. 
Additionally, nearly 90% of all power outages and disturbances have their roots in 
the Distribution Network [7]. While 84% of utilities has substation automation and 
integration underway in 2005, the feeder penetration is still limited to about 20% [6]. 
So, it makes sense to begin Smart Grid at the bottom of the chain, in the Distribution 
Network [7]. 



The scope of this thesis is limited to the communications networks in the 
Distribution Network of the Smart Grid to address the aforementioned gaps. In other 
words, the focus is on the "last mile" communications segment. This thesis 
documents the results of a thorough survey of technical papers and governmental 
agencies' reports then provides the author's critical analysis of communications 
architectures and technologies for Smart Grid Distribution Network. 

1.2 Organization of Thesis 

This thesis is organized into chapters. Chapter 2 covers Smart Grid 
objectives, functions and benefits. Chapter 3 describes data collection in the 
Distribution Network for both end-users and service providers' usage. Chapter 4 
addresses the needs for communications networks in the Distribution Network. 
Chapter 5 discusses five communications architectures. Chapter 6 provides an 
overview of wireline and wireless technology options. Lastly, chapter 7 describes the 
analysis methodology and presents three dimension comparison matrix with a 
conclusion. 



2. What is Smart Grid? 

The United States of America and several other countries have made it a 

national strategic goal to modernize their electric grid [8] to make it more robust, 

secure, expand overall control and make it capable of supporting renewable energy 

resources and anticipated growth demand. Many definitions of Smart Grid (SG) exist 

all around the world [9]. Smart Grid is the modernization and automation of the 

electric power grid changing from a producer-controlled network to one that is less 

centralized and more consumer-interactive and is more than just "smart meters". The 

use of two-way communications and advanced control capabilities will result in the 

realization of a host of benefits and new applications. One can think of SG as an 

Information and Communication Technologies (ICT) based power system [9]. The 

National Institute of Standards and Technology (NIST) defines the Smart Grid as: 

a modernization of the electricity delivery system so it monitors, protects and 
automatically optimizes the operation of its interconnected elements - from 
the central and distributed generator through the high-voltage network and 
distribution system, to industrial users and building automation systems, to 
energy storage installations and to end-use consumers and their thermostats, 
electric vehicles, appliances and other household devices [9]. 

In general, all definitions refer to an advanced power grid through the use of digital 

computing and communications technologies [8]. 



2.1 Recent American Laws Driving Smart Grid Deployment 

Starting with the Energy Policy Act of 2005 (EPACT 2005) Section 103 
titled "Energy Use Measurements and Accountability" that established a deadline of 
October 1, 2012 for all federal building to have some sort of advanced meters that 
provide data of the electricity consumption [10]. Additionally, EPACT 2005 Section 
1252 titled "Smart Metering" obligates electric utilities to supply each of its 
customers upon request, a time-based rate schedule. 

On December 19, 2007, the United States Congress passed the Energy 
Independent and Security Act (EISA) of 2007 into law that mandated the 
modernization of the electric grid with an end goal of Smart Grid [1]. Finally, the 
American Recovery and Reinvestment Act of 2009 (ARRA) included $10 billion in 
investments to encourage transformation to a smarter grid [8]. All these federal laws 
brought visibility and attention to the need for modernizing the electric grid. 
Additionally, several states and electric utilities initiated infrastructure deployments 
in preparation for Smart Grid. Common deployments include the installation of 
advanced meters by utilities companies and Smart Grid test beds as the case with 
Xcel's project in Boulder, Colorado known as "SmartGridCity". 



2.2 Smart Grid Functions and Goals 

In December 2007, the Energy Independence and Security Act (EISA) was 
signed into law. This law established clear national goals to implement Smart Grid. 
Some of the stated benefits include: 

• Self-healing from power disturbances 

• Enables active participation by consumers in "demand response" 

• Operates resiliency against physical or cyber attack 

• Provides power quality for 21st century needs 

• Accommodates all generation and storage options 

• Enables new products, services, and markets 

• Optimizes assets and operational efficiency 

A Smart Grid provides the flexibility to adapt to a changing mix of demand- 
side resources, including changeable load, dispatchable distributed generation and 
storage, as well as output local generation such as wind and solar [6]. Smart-grid- 
enabled distributed controls within the electric delivery system will aide in 
dynamically balancing electrical supply and demand, thus resulting in a more 
adaptable system to imbalances and limit their propagation when they occur [6] . A 
Smart Grid is needed at the distribution system to manage voltage level, reactive 



power, potential reverse power flows and power conditioning, which are critical to 
running grid-connected Distributed Generation (DG) systems [6] . 

Table 2. 1 provides a side by side comparison of key attributes of the existing 
electric grid and the Smart Grid, which is also referred to as "Intelligent Grid". There 
is clear need for Smart Grid at the distribution level to manage: voltage levers, 
reactive power, potential reverse power flows and power conditioning [6]. 
Table 2.1: The Existing Grid vs. The Smart Grid [7] 



Existing Grid 


Smart Grid 


Electromechanical 


Digital 


One -Way Communication 


Two-Way Communication 


Centralized Generation 


Distributed Generation 


Hierarchical 


Network 


Few Sensors 


Sensors Throughout 


Blind 


Self-Monitoring 


Manual Restoration 


Self-Healing 


Failures and Blackouts 


Adaptive and Islanding 


Manual Check/Test 


Remote Check/Test 


Limited Control 


Pervasive Control 


Few Customer Choices 


Many Customer Choices 



The expected functions of Smart Grid are detailed in [1 1] and summarized below: 

• Operation Reliability and Blackout Prevention 

• Condition Monitoring and Asset Management 

• Protection and Station Automation 

• Distribution Network Management 



• Distribution Network Automation 



• Smart Metering 



2.3 Smart Grid Benefits 

The benefits of Smart Grid show up in many areas including the 
infrastructure management and protection, the gained efficiency, economic benefits 
for the consumer and reducing business losses from blackouts. Data from wide-area 
measurement system could have eliminated the $4.5 billion in losses as a result of 
the 2003 blackout of the eastern U.S. and Canada [6]. Another study results show 
that Smart Grid technologies would reduce power disturbance costs to the U.S. 
economy by $49 billion per year [12]. Table 2.2 provides an average estimated cost 
of one-hour power interruption for selected enterprises businesses. 

Table 2.2: Cost of One-hour Service Outage [12] 



Industry 


Average Cost of 1-Hour Interruption 


Cellular communications 


$41,000 


Telephone ticket sales 


$72,000 


Airline reservation system 


$90,000 


Semiconductor manufacturer 


$2,000,000 


Credit card operation 


$2,580,000 


Brokerage operation 


$6,480,000 



Smart Grid can enable reduced overall energy consumption through 
consumer education and participation in energy efficiency and demand response/load 
management programs [13]. Additionally, shifting electricity use to less expensive 
off-peak hours can optimize use of existing power generation that could add $5 
billion to $7 billion per year back into the U.S. economy [12]. Smart Grid would 
reduce the need for huge infrastructure investments between $46 billion and $117 
billion over the next 20 years [12]. The Federal Energy Regulatory Commission 
(FERC) study reported that a moderate amount of demand response could save about 
$7.5 billion annually [14]. Finally and most recently, EPRI prepared a new set of 
cost of power interruption and power quality estimates ranging from $119 billion to 
$188 billion per year [15]. 



10 



3. Data Collection in The Distribution Network 

At the Distribution Network and end-user levels, there are opportunities for 
automation and advanced data collection [16]. There are two methods for 
gathering end-user data: Automated Meter Reading (AMR) and Automated 
Metering Infrastructure (AMI). AMR enables the electric utility to remotely read 
power meters. But it does not address the major issue utilities need to solve, 
which is demand-side management [7]. On the other hand, AMI is much more 
powerful since it is the basic building block for a two-way communications 
between the end users and utilities operators [16]. As described in [17], an AMI 
system consists of four main components: 

• Smart digital meter, which functions as premise gateway 

• Home portal that offers display of information from the gateway 

• Neighborhood access point that aggregates end-users data before 

transmitting it to the substation 

• Central office (usually a substation) where all customers' data is 

aggregated. 
There is often a reference to an AMI meter, which is defined as a digital meter 
with two-way communications, automated meter data collection, outage 
management, dynamic rate structures and demand response for load control [17]. 



11 



Managing Smart Grid metering data is difficult due to the sheer size and 
complexity of the number of data point [18]. Useful data in the Distribution 
Network can be classified as: consumer specific data or device and control data. 
Each of these data types is explained in the next two sections. 

3.1 Consumer Energy Usage Data 

Smart meter system involves large amount of data transfer between the 
utility company, smart meter and home appliances connected to the network [19]. 
The smart meter data will be used by the utilities operators for further analysis, 
control and real time pricing method [20]. The customer gateway will interact 
with all smart appliances and the Distribution Network and functions: integrated 
operation and control of supply and demand and demand response [21]. 

3.2 Device Status Data and Control 

A major benefit of Smart Grid containing renewable Distributed Generation 
(DR) is the possibility of forming islands when separation from the main electric 
system occurs due to fault condition or system failure [22]. So, continuing to 
communicate with the islanded section of the grid is required. Table 3.1 provides 
a sample of the data requirements. 



12 



Table 3.1: Sample Data Requirements [22] 



System 


Inputs 


Outputs 


Computed Values 


Component 








Breakers 


Breaker Status 


Breaker Status 




Switches 


Enable/Disable 


Voltages 




Protective 




Currents 




elements (Fuses) 








Generators: 


Enable 


Voltages 


Power Quality 


Wind 


Dispatch 


Currents 


Availability 


Solar (PV) 




Phase 


Health index 
Power 


Transformers 


Tap Positions 


Temperature 

Pressure 

Gas, 

Vibration 

Noise 


Reliability 


Lines 


Enable/Disable 


Voltages 


Real Power 






Currents 


Reactive Power 


Reactive Power 


Status 


Voltages 


Power Quality 


Elements 


Enable/Disable 


Currents 




Loads: 


Status 


Voltages 


Power Quality 


Active 


Enable/Disable 


Currents 




Passive 


Rate (Tier 
Demand 
Management) 
Demand 







As explained in [21], devices in the Distribution Network include the 
Distribution Automation System (DAS) and the Meter Data Management System 
(MDMS). The customer's gateway interacts with the DAS for integrated 
operation and control of supply and demand of electricity. Where the MDMS 
collects and stores data from customers and provide them to the utilities 



13 



operators for accounting and customer service [21]. The customers will be able to 
schedule appliances' operation and request loads using real time pricing data, 
thus reducing electricity usage during peak hours, which benefits both end users 
and utilities. 



14 



4. Communications for The Distribution Network 

4.1 The Need for Communications 

Without a robust communication system in the Distribution Network, only 
parts of the Smart Grid vision could be realized [5]. The Smart Grid is all about 
extending remote monitoring and control of devices in the Distribution Network 
and gathering real-time data. All of these functions require two-way 
communications [13]. The Distribution Network is facing increased frequency of 
unpredictable catastrophic events due to limited knowledge and management of 
these complex systems [23]. The current communications system deployed over 
the Distribution Network are oriented to support specific services, so that, the 
development of new services over the DN and the addition of new agents may 
result as very expensive [24] . The original design of Distribution Networks did 
not account for two-way power flows or active demand, hence, changes are 
needed in the way they are designed and operated to realize these functions 
through the use of advanced communications and information technologies [25]. 
Automation and communication infrastructures are needed to enable demand 
response and to make widespread end-user participation possible in support of 
Smart Grid and market operation [26]. 



15 



4.2 Communications Requirements 

A communication system is the key component of the Smart Grid 
infrastructure [20]. Smart Grid communication technologies must allow the 
utility's Control Center access to each connected meter several times a second 
[27]. As detailed in [28], communications network for the energy management 
must provide distinct qualities including: high reliability and availability, 
automatic redundancy, high coverage and distances, supports large number of 
nodes, has low delays, security and ease of deployment and maintenance. 

The various functions of the Distribution Network have different 
requirements for a communications network. For example, meter reading can be 
scheduled for anytime and does not require permanent real-time 
communications. On the other hand, event or fault data must be communicated in 
real-time with maximum allowed delay of 300 milliseconds [21]. Additionally, 
depending on the communications architecture selected, communications among 
adjacent end-users' gateways could be required. Tables 4.1 and 4.2 summarize 
the communications requirements to and from customer's gateway. 



16 



Table 4.1: Communications From Customer's Gateway and Requirements [21] 





Data 


The 
other 




Allowable 


No. 
of 








end 


Frequency 


Delay 


Entry 


Applications 



From 


Request for 


Other 


On 


1 second 


1 


Keeping output 


Customer 


reactive 


customer 


demand 






power of 


Gateway 


power 


Gateway 








distributed 
power 
generation 
during voltage 
regulation 


Measured 


SCADA 


Every 30 


1 minute 


121 


Optimal control 




values for 


system 


minutes 




*1 


of grid 




generation / 










equipment 




consumption 










Power flow 

leveling, 

Demand-supply 

balancing 

Meter reading, 

Customer 

service 


Forecasted 


Twice per 


Several 


192 


Optimal control 




values for 




day 


minutes 


*2 


of grid 




generation / 










equipment 




consumption 













*1: 4 items (active/reactive power of generation/distribution) x30 (Value for 1 minute) + 

Time stamp 

*2: 4 items mentioned above x 48 (data for 1 day) 



17 



Table 4.2: Communications To Customer's Gateway and Requirements [21] 





Data 


The 
other 




Allowable 


No. 
of 








end 


Frequency 


Delay 


Entry 


Applications 
















To 


Request for 


Other 


On 


1 second 


1 


Keeping output 


Customer 


reactive 


customer 


demand 






power of 


Gateway 


power 


Gateway 








distributed 
power 
generation 
during voltage 
regulation 


Event 




At event 


50 ~ 300 


1 


Power system 




information 






milliseconds 




protection 




(e.g. earth 














fault) 


SCADA 

system 










Threshold 


Every 30 


1 minute 




Power flow 




of reverse 




minutes 






leveling, 




power 










Demand-supply 




flow, 










balancing 




Generation 














forecast 












Tomorrow 




Every day 


Several 


48*3 


Optimal control 




tariff 


Tariff 
server 




minutes 




of grid 
equipment 


Current 


Every 30 


1 minute 


1 


Demand 




tariff 




minutes 






response 


DR event 


DR 


Every 1 


10 seconds 


1 


Demand 






server 


minute 






response 


*3: Tariff p 


;r 30 minutes 


x 48 (for 1 d 


ay) 









18 



4.3 Are Smart Grid Standards Required? 

Standards are the first and required step to ensuring interoperability 
between equipment from various vendors and enabling interconnection among 
different users and operators, which are necessary functions in the vast electric 
grid that is owned and operated by hundreds of stakeholders. Standards is an 
important issue that must be resolved before Smart Grid becomes a reality [29]. 
The evidence from other industries indicate that interoperability generates 
tangible and intangible benefits around 0.3% - 0.4% in cost savings and avoided 
infrastructure construction, which could net a $12.6 billion per year in Smart 
Grid benefits [12]. 

Under Section 1305 of EISA, the National Institute of Standards and 
Technology (NIST) has the primary responsibility of coordinating the 
development of framework including protocols and standards for information 
management to achieve interoperability [1]. NIST recognized the urgent need for 
Smart Grid standards by developing a three phase plan to identify existing 
standards as well as the need for new ones [8]. 

4.4 Emerging Smart Grid Standards 

For the Smart Grid to be fully integrated, universal standards must be 
applied [30]. Several well known standards' bodies including the International 



19 



Electrical and Electronics Engineers (IEEE), International Standards 
Organization (ISO), International Electrotechnical Commission (IEC) and 
Internet Engineering Task Force (IETF) are actively developing new standards 
that are required for the proper and secure deployment of Smart Grid. NIST 
identified 16 specifications and 15 standards that are important for Smart Grid 
[8]. Additional standards are under review. There is a consensus on a set of 
standards regarded as core information technology standards for the future 
Distribution Network of a Smart Grid [31]. These standards are listed below [31]: 

• IEC 6 1 970/6 1968: Common Information Model (CIM) 

• IEC 61850: Substation Automation Systems (SAS) and DER (Distributed 
Energy Resources) 

• IEC 6235 1 : Security for the Smart Grid 

• IEC 62357: TC 57 Seamless Integration Architecture 

• IEC 60870: Communication and Transport Protocols 

• IEC 61400-25: Communication and Monitoring for Wind Power Plants 

• IEC 61334: DLMS (Device Language Message Specification (originally 
Distribution Line Message Specification) 

• IEC 62056: COSEM (Companion Specification for Energy Metering) 

• IEC 62325: Market Communications using CIM 



20 



5. Communications Architectures 

Architecture describes how systems and components interact and embodies 
high-level principles and requirements for Smart Grid applications and systems [8]. 
Like the Internet, the Smart Grid is a network of different networks that must interact 
together on regular basis. So, the Smart Grid architecture will be a composite of 
many system and subsystem architectures [8] rather than a single architecture. The 
communication architecture of the future Smart Grid is yet to be defined [32]. The 
rest of this chapter addresses architecture options for the Distribution Network. 

Designing a communication system architecture that meets the Grid's 
complex requirements is essential to the successful implementation of Smart Grid 
[22]. In general, coordination and information exchange between devices can be 
implemented via different communication architectures. Four possible 
communications architectures are illustrated in [33]. 

This thesis report describes five communication architectures for possible 
deployment in the Distribution Network. The Distribution Network is similar to the 
"last mile" problem in the telecommunications network design. In the utility's 
communications network, the "last mile" connects the customer's smart meter to the 
backhaul network as depicted in figure 5.1. Each architecture is covered in the 
remainder of this chapter. 



21 




Figure 5.1: A view of the Utility Information Systems [34] 
5.1 Direct Connect Architecture 

This is most basic architecture where each smart meter has a dedicated 
linear connection to the data hub inside a substation. This setup is often referred 
to as "hub and spoke" network. In this scenario, there are no other devices, like 
aggregators, between the smart meter and the data hub inside the substation. In 
other aspects, this architecture is a star topology with the data hub inside the 
substation has hundreds to thousands of dedicated communication links out to the 
customers' smart meters. Each communication link can be of any medium type: 
wireline or wireless. Due to the large number of smart meters in urban areas, this 
architecture is not attractive. However, it could be a viable option for low 



22 



population density areas. In this case, a single communication link from each 
home to a substation is low cost and does not require an elaborate 
communications infrastructure build or aggregators. Depending on the selected 
communication media type, this architecture has limitation. Figure 5.2 depicts the 
main components of this architecture. 



Key: 

Communication Link 
(wireline or wireless) 



Backbone 
Communication Link 



Sub-station 




Figure 5.2: Direct Connect Architecture 
5.2 Local Access Aggregators Architecture 

The essence of the Local Access Aggregators architecture is aggregating 
smart meters data at a neighborhood level before transmitting it to a data hub 



23 



inside the substation. The aggregator device sits between the smart meters and 
the data hub inside the substation. This model builds on the Neighborhood 
Access Network (NAN) where NAN ensures communications between the smart 
meter and the data aggregators [35]. The concept of NAN is recent and as such 
no standard NAN definition yet exists [17]. In general, the NAN aggregator 
connects with the customer home network on one end and with the Wide Area 
Network (WAN) on the substation end as illustrated in figure 5.3. 




Figure 5.3: Overview of AMI Network with NAN 
This architecture has advantages over the direct connect architecture because 
it reduces the number of dedicated communication links to the substation and 
benefits from data aggregation at the neighborhood level thus optimizing the 



24 



communications links into the substation by using trunks. Additionally, the ability to 
collect and process data locally will not only reduce communication bandwidth 
requirements, but also reduce vulnerability to hacker attacks and reduce cyber 
security concerns [16]. 



Key: 

Communication Link 
(wireline or wireless) 

Backbone 
Communication Link 

Trunk 
Communication Link 



Sub-station 




Figure 5.4: Local Access Aggregator Architecture 
Figure 5.4 shows main segments of this architecture including: smart meter 
at the premise, aggregator in the neighborhood installed on a structure that is 
owned by the utilities e.g., pole or cabinet and data hub inside the substation. 



25 



5.3 Interconnected Local Access Aggregators Architecture 

This architecture is similar to the previous architecture with one exception, 
which is adjacent NAN networks have interconnected trunks as shown in figure 
5.5. These additional communication trunks provide redundancy for the 
aggregators thus allowing more routes to communicate with the substation's data 
hub and enable local communications among NANs should communication trunk 
with the substation is lost. This last feature is important for effective sharing of 
Distributed Generation (DG) resources available in adjacent neighborhoods 
during an islanding situation. 



Key: 

Communication Link 
(wireline or wireless) 

Backbone 
Communication Link 

Trunk 
Communication Link 

Aggregator to Aggregator _ 
Communication Link 



■< ► 



Sub-station 




Figure 5.5: Interconnected Local Access Aggregators Architecture 



26 



5.4 Mesh Architecture 

This architecture builds on the previous one with additional degree of 
connectivity at the smart meters' level in addition to the aggregators' level as 
shown in figure 5.6. Because of the additional required communication links 
among smart meters that are do not have wireline connections, wireless Radio 
Frequency (RF) technology is well suited for interconnecting smart meters in a 
particular area. 



Key: 

Communication Link 
(wireline or wireless) 

Backbone 
Communication Link 

Trunk 
Communication Link 



Aggregator to Aggregator -^- 
Communication Link 

Meter to Meter 
Communication Link 



Sub-station 




Figure 5.6: Mesh Architecture 



27 



Additionally, RF has the ability to dynamically establish ad hoc 
communications links between adjacent networks [36]. Another advantage is that 
communications range can be increased by establishing multiple hops until 
reaching the final destination. RF mesh operates in the unlicensed Industrial 
Scientific and Medical (ISM) frequency band ranging from IEEE 802.11 
Wireless Local Area Networks (WLAN), Wi-Fi, Bluetooth and Microwave [20]. 
This fact makes RF less attractive for use in Smart Grid application due to high 
possibility of interference with commonly deployed private networks. Another 
disadvantage that is common to wireless communications is security concerns. 
However, strong data encryption is an effective way to remedy such security 
issues. 

The wireless-wired architecture is the most popular approach and has been 
adopted in some pilot projects where smart meters in the neighborhood 
communicate with an aggregator through a wireless mesh network and the 
aggregator communicates with the central management facility through wired 
communication [37]. 

5.5 The Internet Cloud Architecture 

The premise of this architecture is leveraging the customer's existing 
Internet service as a communication link between the end user and the utilities 



28 



operator. The majority of houses subscribe to Internet service where service is 
available. Rural areas are the exception since Internet service is not always 
available. Under this architecture, the smart meter uses the existing Internet 
connection inside the house as a communication link via Ethernet port or Wi-Fi 
to transmit information to a utilities' server that most likely is hosted in a data 
center. The biggest advantage of this architecture is low cost since no additional 
monthly charges for communications are required. Another big advantage is for 
the utility companies since customers' data can be easily stored on servers 
without having expensive aggregators in the neighborhoods or inside the 
substation. Of course, the assumption is customers already have Internet service 
or can get it. 

This architecture has many benefits including low cost for the customer by 
leveraging an existing Internet service and quick deployment due to minimal 
infrastructure build. It also allows for both peer to peer communications as well 
as centralized decision capability. This architecture facilitates the use of "cloud" 
services to gather, store, and analyze huge volumes of data and make it available 
for those with appropriate level of access. 



29 



Key: 

Internet Communication Link 
(wireline or wireless) 

Backbone 
Communication Link 

Trunk Internet 
Communication Link 



Sub-station A 



Sub-station B 




Figure 5.7: The Internet Cloud Architecture 



30 



6. Technology Options 

Both wireline and wireless communication technologies are possible 
deployment options for Smart Grid. Some of the popular communication 
technologies are Power Line Communications (PLC), cellular, licensed and 
unlicensed radio, existing internet connection, Wi-Fi and WiMAX [19]. In 
certain situations, wireless technology have advantages over wired technologies, 
such as low cost and ease of connection but suffers from interference and signal 
attenuation [20]. On the other hand, wireline communication technologies are 
more reliable, less prone to interference, but very expensive to deploy especially 
if new infrastructure is required. Wired communication network can be 
established for smart meters, but it will be complicated and expensive solution, 
while wireless communication network can be implemented even on ad-hoc basis 
[38]. The Smart Grid, as a complex system, requires a heterogeneous 
communication technologies to meet its diverse needs [32]. 

6.1 Wireline Technology Options 

Wireline communication media include: twisted pair copper cables, coaxial 
cables, power line and fiber optic cables. Each of these media types has unique 
characteristics that will be discussed in the remainder of this section. 



31 



Twisted Pair (TP) copper cables are the traditional telephone wiring, which 
are present in almost every home and connect back to a telecommunications 
carrier Central Office (CO). These copper wires have varying specifications and 
quality that is determined by their age. Unshielded Twisted Pair (UTP) is older 
cable that is prone to cross talk and interference. However, Shielded Twisted Pair 
(STP) is newer cable type that is less prone to cross talk and interference. 
Additionally, these wires are usually configured in a star topology where 
hundreds of homes and buildings have dedicated connections back to the 
carrier's CO. Hence, the existing cables would not support mesh architecture 
based on their physical routes. Hence, mesh requires placing additional cables, 
which is very expensive and takes a long time to deploy. 

Coaxial cable is another wireline media type. These cable plants are used 
by cable companies to provide video services and in recent years voice and data. 
The cable plant is shared resource in a single neighborhood and as such shares 
bandwidth. This architecture has two fundamental issues: lower data rates during 
peak usage hours in densely populated areas especially for those customers 
located at the end of the cable route in a neighborhood and presents security 
concerns for customer's confidential data since the main cable is a shared 
medium in the last mile segment. With the introduction of DOCSIS 3.0, cable 
companies are offering Internet services using coaxial cable with high bandwidth 



32 



rates, but it is still a shared bandwidth. Additionally, coaxial cables presence is 
limited to metropolitan areas and rarely found in rural areas. 

Fiber Optics is the most advanced wireline media type with many superior 
characteristics like extremely high data rates, long distance reach and immunity 
from electromagnetic interference. There are two types of optical fiber cables: 
Single Mode (SM) and Multi Mode (MM) fiber. SM is used for long distances, 
while MM is used for short distances less than two kilometers. The trend is to use 
SM fiber for most applications. However, fiber optic cables are the most 
expensive wireline media type to install and the least widespread in homes and 
buildings. Most new buildings and homes are wired with fiber optic cables. New 
deployments include Fiber-To-The-Home (FTTH) or Fiber-To-The-Premise 
(FTTP), which typically use Gigabit Passive Optical Network (GPON). GPON is 
a network architecture that uses a point-to-multipoint scheme to serve multiple 
buildings. Encryption is used in this shared environment to ensure data security. 

Power lines represent the densest network in this country, where every 
building has a power line connection and power line termination [39]. As such, 
Power Line Communication (PLC) system appears to be well suited to 
implement the Smart Grid network [40], [41]. These power lines can be used to 
transmit Smart Grid data from the home back to the substation directly. This is 
the most direct wireline media connecting the end-user with the substation. PLC, 



33 



under normal operations, has an advantage that all smart meters can be reached 
as opposed to a wireless solution where 100 percent service coverage is not 
always possible [42]. However, using power lines for communications has its 
drawbacks. First, the interference issues around high voltage power lines and the 
need to bypass transformers where a bridge device is used to bypass the 
transformer. Using power lines is preferred by utility companies since they will 
have total control of the communication link from the substation to the end 
customer and do not need to rely on third party providers for this communication 
network. The biggest issue with using power lines for Smart Grid communication 
is losing this vital communication network during electric power lines being 
down, yet this is the time when communication is needed the most. Power line 
cuts will stop communications with the isolated areas and as such make it 
impossible to gather data, isolate problems and attempt to solve the problem 
quickly. Simply put, under this condition, Smart Grid objective for the 
Distribution Network won't be achieved. 

Table 6.1: Qualitative Characteristics of Wireline Communication Media Types 



Wireline Media 


Data Rate 


Distance Reach 


Existing Geographic Coverage 


Twisted Pair (TP) 


high 


long distance 


high 


Coax cable 


high 


medium distance 


low 


Power lines (PLC) 


high 


high distance 


high 


Fiber Optic Cable 


very high 


very long distance 


limited 



34 



6.2 Wireless Technologies 

Wireless technology is very attractive for Smart Grid deployment. In 
general, it is much faster to deploy than wireline medium due to minimal 
construction areas when compared with digging streets to deploy new conduit 
system and pull cables through it. Using wireless communications has many 
benefits [43]. Several wireless technology options, either licensed or unlicensed 
frequencies are available. Most popular technologies include: Satellite, 
microwave, WiMAX, cellular, Wi-Fi and Zigbee. 

Satellite is the most expensive wireless technology and supports relatively 
low data rates. It is not suitable for general deployment in the distribution 
network, but may have role in the transmission segment. The signal receiver on 
the ground must be within the satellite coverage footprint. There is limited 
number of satellite operators or service providers due to high deployment cost of 
these systems. Additionally, latency is a big issue due to large distances a signal 
must travel from ground to the satellite and back to earth. 

Microwave is based on licensed frequencies that are controlled by the 
Federal Communication Commission (FCC). These frequencies are limited and 
require line-of-sight between transmitter and receiver to operate. As such, 
depending on the terrain, they usually require tall tower structure to meet line-of- 



35 



sight requirement. Microwave is not suitable for wide deployment in the 
Distribution Network. However, it may have limited and targeted application in 
rural areas where no other communications medium is available. 

WiMAX stands for Worldwide Interoperability for Microwave Access that 
focuses on fixed wireless applications and is based on IEEE 802.16 standard. It 
supports data rates up to 72 Mb/s and a range up to 6 miles. Earlier version of the 
WiMAX standard requires line-of-sight, but not later version [11]. Additionally, 
WiMAX has limited deployment in the United States and it will be expensive to 
deploy an extensive WiMAX network to meet Smart Grid requirements in the 
Distribution Network. 

Wi-Fi stands for Wireless Fidelity, which is a trademark of the Wi-Fi 
Alliance [44]. It is based on IEEE 802.11 standard and operates in the unlicensed 
2.4 GHz Industrial Scientific and Medicine (ISM) band and has reach from 20 
feet indoors to about 300 feet outdoors with the potential for even longer reach. It 
is widely used in home networks and several deployments by local municipalities 
to cover a citywide. Because Wi-Fi networks are common for use in-home 
applications and use unlicensed spectrum, interference is a big concern. 
Additionally, reach is limited and is not suitable for communications in the 
Distribution Network. 



36 



Zigbee is a low-power wireless protocol that operates in the unlicensed 
Industrial Scientific and Medicine band of 2.4 GHz. It is based on IEEE 802.15.4 
standard. Zigbee, WirelessHART and ISA 100.11a are three protocols that use 
the 802.15.4 PHY standard but define their own Media Access Control (MAC) 
and network [11]. Zigbee and Zigbee Smart Energy Profile (SEP) have been 
realized as the most suitable communication standards for Smart Grid residential 
network domain by NIST [20]. However, they are not suitable for deployment in 
the Distribution Network due to short reach and serious security issues. 

Cellular is a radio network distributed over a geographic area called cells. 
Cellular networks has several advantages including increased capacity, reduced 
power use, large coverage area and reduced interference from other signals 
through spectrum reuse. Initial roll out of cellular service is called first 
generation (1G), which is an analog signal followed by second generation (2G), 
which is a digital service followed by third generation (3G) and most recently 
fourth generation (4G). There is 2.5G, which is based on either General Packet 
Radio Service (GPRS) or Enhance Data Rates for GSM Evolution (EDGE). 
GSM is the abbreviation for Global System for Mobile Communications. While 
EDGE is still available in fringe areas not upgraded to 3G, GPRS have been 
mostly replaced by 3G networks [11]. The 3G and 4G technologies support 
higher data rates and faster service. Currently, select wireless communications 



37 



providers deployed 4G networks. Cellular service is very attractive for use in the 
Distribution Network due to its widespread coverage. The broadband wireless 
communications technology has many inherent advantages when used in Smart 
Grid [45]. The qualitative summary in Table 6.2 is the result of combining 
wireless technology specifications presented in [20] and qualitative analysis 
presented in [11] except for satellite and microwave technologies. 

Table 6.2: Qualitative Characteristics of Wireless Communication Technologies 



Technology 


Data Rate 


Distance Reach 


Existing Geographic Coverage 


Satellite 


high 


high 


high 


Microwave 


high 


high 


low 


Cellular (2.5G) 


low 


high 


good 


Cellular (3G) 


medium 


high 


good 


Cellular (4G) 


high 


high 


good 


WiMAX 


high 


high 


low 


Wi-Fi 


high 


low 


low 


Zigbee 


low 


low 


low 



38 



7. Analysis Methodology and Approach 
7.1 Metrics 

The success and failure of the Smart Grid rests on a communication 
system that is intelligent, secure, reliable and cost effective [16]. The communication 
network for the Smart Grid requires data transfer in a timely manner with adequate 
bandwidth and reliability [3] via two-way communication with low latency. 
Communication technologies for Smart Grid must be cost efficient, provide good 
transmittable range, excellent security features and adequate bandwidth [19]. 
Additionally, the selection of a communication technology should be based on 
several criteria including: bandwidth requirement, topology of network, reliability, 
security, feasibility of solution [33]. 

Based on the aforementioned discussion and general communication 
network design guidelines, the following criteria are selected for comparing the 
communication architectures described in chapter 5 and the wireline and wireless 
communication technologies presented in chapter 6. 

a) Bandwidth or Data rate: bandwidth often refers to a data rate measured in bits 
per second. For digital signals, bandwidth is the data speed or rate, measured in 
bits per second (bps). Various parts of the Smart Grid have different bandwidth 
requirement [46]. A communications throughput of (2 - 5) Mb/s was estimated 
as a guideline for Smart Grid link to allow for transmitting voltage and current 



39 



measurements for three phases, phase amplitude, phase angle as well as 
additional information like meter identification and overhead packets [22]. 

b) Latency: latency is a measure of time delay experienced in a communications 
network. It can be measured as one-way, the time it takes a sender to transmit 
data to the destination receiving it, or round trip, which is the time it takes for 
data to travel from the sender to the receiver and back to the sender. Information 
concerning faults on the Smart Grid must be transferred from the DAS to a 
customer gateway with the shortest possible latency and must be completed 
within 50 ms and communication involving a request for reactive power has the 
second strictest latency requirement [21]. Both rural islanding and urban meshed 
distribution scenarios have tolerance for a maximum of six cycles or 100 ms 
[22]. This requirement imposes even stricter requirement on the communications 
network. Latency in a WiMax link is 10 ms from the smart meter to the base 
station, so, the communication network must be carefully designed to ensure the 
latency end-to-end is less than 50 ms [22]. Also, Long Term Evolution (LTE), 
which is 4G wireless technology enjoys similar latency characteristics as WiMax, 
with latency of (5-10) ms [22]. 

c) Security: network security is extremely important to ensure all customers data 
remain private and no unauthorized access to the network. Several techniques 
including user authentication, access control authorization and data encryption 



40 



are usually implemented to ensure network security. Because a wireless network 
uses broadcast medium, it must be resistant to tampering of messages, preserving 
confidentiality of information and prevents unauthorized access [11]. In general, 
wireline medium is more secure than wireless media, but Smart Grid requires a 
higher level of security. The legacy cyber security techniques for enterprise 
networks can hardly fit well for Smart Grid requirements to operate securely in 
the public data communication networks like the internet [47]. 

d) Scalability: is the ability of a system or network to handle expansion without the 
need for replacing major segments of the network. In the case of Distribution 
Network, the network must be flexible to accommodate high volumes of smart 
meters connecting new houses and businesses. 

e) Resilience: is the ability of a network to function properly during interference 
either random or intentional. In order for a network to be resilient, it must be 
capable of continued operation even in the presence of localized faults [48]. In 
this respect, mesh architecture provides the maximum resiliency due to multiple 
paths to get between nodes. 

f) Reliability: is the ability of a network to perform within its normal operating 
parameters to provide a specific level of service. Reliability can be measured as a 
minimum performance rating over a specified interval of time. In general, 



41 



availability for communication networks ranges from 99.9% (3 nines 
reliability). to 99.999% (5 nines reliability). 

g) Interoperability: means devices and services from multiple vendors are 
compatible with each other and can be integrated into a generic network. 
Interoperability is very important consideration in network deployment. Ensuring 
devices and subsystems are interoperable is of high importance to ensure Smart 
Grid goals are achieved. Standards are key enabler to achieve interoperability. 
For communications in the Smart Grid to be truly effective, they must exist in a 
fully integrated system and to be fully integrated, universal standards must be 
applied [30]. Hence, the urgency for developing and updating many standards to 
encourage Smart Grid deployment. 

h) Distance Reach: each wireline and wireless communication technology has its 
unique signal reach distances. Signal reach ranges from few meters to tens of 
kilometers depending on the technology. Terrain characteristics affect wireless 
signal reach and as such must be considered during technology evaluation stage. 

i) Existing Geographic Coverage: the electric Distribution Network covers vast 
geographic areas with varying terrain characteristics. Selecting technologies that 
already cover the areas where Smart Grid will be deployed can reduce the 
deployment cost. However, a single technology may not provide all coverage in 
all area. 



42 



j) Cost of Ownership: capital expenditure (CAPEX) and operation expenditure 
(OPEX) are practical considerations when designing any network. Given the high 
numbers of smart meters requiring communications infrastructure, low CAPEX 
and OPEX will be key for early adopters of Smart Grid. 

7.2 Analysis Methodology 

The methodology used to compare the architectures, technologies and metrics 

for suitability in the Smart Grid Distribution Network is: 

A) identify key communications architectures 

B) select viable communications technologies 

C) choose applicable metrics 

D) assign weighting factors using the following scale from highest to lowest: 
good fit = 3, moderate fit = 2, poor fit = 1 and not suitable = 0. 
Additionally, the following metrics guidelines were adopted from [11]. 

Table 7.1: Metrics Guidelines [11] 





Ave. Data Rate 


Ave. 
Latency 


Distance Reach 


Scalability 


Good 


>1.5Mb/s 


< 250 ms 


> 1000 meters 


> 1000 nodes/ data 
hub 


Moderate 


500Kb/s- 1.5 

Mb/s 


250 ms - 1 
sec 


(100 - 1000) 
meters 


(100 - 1000) nodes/ 
data hub 


Poor 


< 500 Kb/s 


> 1 sec 


< 100 meters 


< 100 nodes/ data 
hub 



E) summarize the results in a multi dimension matrix 



43 



7.3 Summary of Results 

Each technology option is analyzed against the five architectures using 
the selected ten metrics. The result is a three dimension matrix. Then normalize 
the total score for each architecture and technology combination and select the 
top five scores representing the best overall solutions. The next series of tables 
present the detailed scores for each architecture, all wireline and wireless 
technologies against the ten criteria. 

Table 7.2 provides summary of architecture 1 scenarios. Most wireless 
technologies and one wireline technology i.e., power line communication are 
suitable for this architecture since power lines already exist between the end user 
facility and the utilities substation. However, copper twisted pairs, coax and fiber 
optic cables do not exist and as such require significant installation and are very 
expensive, which excludes them to be practical options for architecture 1. 
Satellite service is very expensive to deploy and maintain in addition to high 
monthly charges. Microwave communication network requires valuable and 
scarce spectrum and significant capital investment to build such infrastructure. It 
requires line-of-sight (LOS) between transmitter and receiver. Hence, microwave 
is not suited for architecture 1 especially in residential areas. WiMAX also 
requires large capital investment to build a network that covers all residents in 
the U.S.A. Wi-Fi lacks the required distance reach and geographic coverage. 



44 



Some cities across the country partnered with private providers to build a 
citywide Wi-Fi network. However, these examples are rare and a countrywide 
Wi-Fi coverage won't be cheap to build nor practical. Zigbee is an in-home 
network that will communicate with smart devices within a household. Hence, it 
has very short distance reach, which makes it not suitable for Smart Grid 
communication in the Distribution Network. For architecture 1, the best overall 
options are those using cellular technology with 4G being the best since it 
supports the higher data rates. 

Table 7.2: Summary of Architecture 1 Metrics 



Criteria 


Architecture #1 (Direct Connect) 


Wireless 


Wireline 


B 
"55 


CD 
> 
CO 

2 

o 

2 


io 
£L 

CO 

"55 
O 


5" 

CO 

1— 
CB 

_3 

"55 
O 


CD 

CO 

"55 
O 


X 

< 


CD 

_o 

N 


Ll 


H 
h_ 
'CO 
0- 
"O 

a> 
to 

1 


.o 

CO 

O 
« 

X 

CO 

o 
O 


O 

_i 
Q. 


CD 
.O 
CO 

O 
o 

Q. 

O 

CD 
.O 

Ll 


Bandwidth / Data Rate 


3 


3 


1 


2 


3 


3 


1 


3 


3 


3 


2 


3 


Latency 


1 


2 


2 


2 


1 


3 


1 


3 


3 


3 


3 


3 


Security 


3 


3 


2 


2 


3 


3 


2 


2 


3 


2 


2 


3 


Scalability 


1 


1 


2 


3 


3 


3 


1 


1 


1 


1 


3 


1 


Reliability 


2 


2 


2 


2 


2 


2 


1 


2 


3 


3 


2 


3 


Interoperability 


2 


2 


2 


2 


2 


1 


1 


3 


3 


3 


2 


2 


Resilience 


2 


2 


3 


3 


3 


3 


2 


1 


3 


3 


3 


3 


Distance Reach 


3 


3 


3 


3 


3 


3 





1 


2 


2 


2 


3 


Existing Geographic Coverage 


2 





2 


2 


2 

















1 





Cost of Ownership 


1 


1 


3 


3 


3 


1 


1 


1 


1 


1 


2 


1 


Sum of points: 


20 


19 


22 


24 


25 


22 


10 


17 


22 


21 


22 


22 


Max. No. of Points 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


Normalized Score: 


67% 


63% 


73% 


80% 


83% 


73% 


33% 


57% 


73% 


70% 


73% 


73% 



45 



Table 7.3 presents summary of architecture 2 scenarios. The discussion 
for architecture 1 listed above applies here as well. Hence, the best overall 
technology options are those using cellular technology with 4G being the best 
option since it supports the higher data rates. However, 4G is not available in all 
areas and some areas may be limited to 3G or 2.5G only. Moreover, some remote 
areas may not have any cellular service, so in these cases, PLC can be a viable 
wireline option. 

Table 7.3: Summary of Architecture 2 Metrics 



Criteria 


Architecture #2 (Aggregator) 


Wireless 


Wireline 


B 
"55 

03 

to 


cd 
> 

CO 

2 

o 

2 


CD 
io 

£i 

co 

_3 

"55 
O 


5" 

CO 

cfl 

_3 

"55 
O 


3" 

CO 

"55 
O 


X 

< 


CD 

a> 
_o 

O) 

N 


Ll 


H 

'CO 
Q. 
"O 

a) 
to 

1 


.Q 
CO 

O 
re 

X 

CO 

o 
O 


O 

_i 
Q. 


.a 

CO 

O 
o 

Q. 
O 

CD 
.O 

Ll 


Bandwidth / Data Rate 


3 


3 


1 


2 


3 


3 


1 


3 


3 


3 


2 


3 


Latency 


1 


2 


2 


2 


1 


3 


1 


3 


3 


3 


3 


3 


Security 


3 


3 


2 


2 


3 


3 


2 


2 


3 


2 


2 


3 


Scalability 


1 


1 


2 


3 


3 


3 


1 


1 


1 


1 


3 


1 


Reliability 


2 


2 


2 


2 


2 


2 


1 


2 


3 


3 


2 


3 


Interoperability 


2 


2 


2 


2 


2 


1 


1 


3 


3 


3 


2 


2 


Resilience 


2 


2 


3 


3 


3 


3 


2 


1 


3 


3 


3 


3 


Distance Reach 


3 


3 


3 


3 


3 


3 





1 


2 


2 


2 


3 


Existing Geographic Coverage 


2 





2 


2 


2 

















1 





Cost of Ownership 


2 


1 


3 


3 


3 


1 


1 


1 


1 


1 


2 


1 


Sum of points: 


21 


19 


22 


24 


25 


22 


10 


17 


22 


21 


22 


22 


Max. No. of Points 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


Normalized Score: 


70% 


63% 


73% 


80% 


83% 


73% 


33% 


57% 


73% 


70% 


73% 


73% 



46 



Table 7.4 depicts scenarios for architecture 3. Once again, the same 
analysis for architectures 1 and 2 applies here with one exception. Power line 
communication is not as favorable for architectures 3. Under architecture 3, 
additional power lines are required to interconnect the Aggregators since the 
power lines are radial by design. This fact will increase the cost of ownership for 
PLC technology under this architecture. 

Table 7.4: Summary of Architecture 3 Metrics 



Criteria 


Architecture #3 (Interconnected Aggregators) 


Wireless 


Wireline 


3 
"55 

CO 


CD 

> 

CO 

S 

2 

o 

2 


C5 

m 

cvi. 

CO 

"55 
O 


(D 

CO 

v. 

CO 

"55 
O 


(D 

CO 

"55 
O 


X 

< 


CD 
CD 

_o 

O) 
N 


Ll 


H 
s— 
'CO 
Q. 

"D 
0) 

to 

h- 


.a 

CO 

O 

To 

X 

CO 

o 
O 


O 
0. 


a> 
.o 

CO 

O 
.o 

Q. 
O 

55 
.o 

Ll 


Bandwidth / Data Rate 


3 


3 


1 


2 


3 


3 


1 


3 


3 


3 


2 


3 


Latency 


1 


2 


2 


2 


1 


3 


1 


3 


3 


3 


3 


3 


Security 


3 


3 


2 


2 


3 


3 


2 


2 


3 


2 


2 


3 


Scalability 


1 


1 


2 


3 


3 


3 


1 


1 


1 


1 


3 


1 


Reliability 


2 


2 


2 


2 


2 


2 


1 


2 


3 


3 


2 


3 


Interoperability 


2 


2 


2 


2 


2 


1 


1 


3 


3 


3 


2 


2 


Resilience 


2 


2 


3 


3 


3 


3 


2 


1 


3 


3 


3 


3 


Distance Reach 


3 


3 


3 


3 


3 


3 





1 


2 


2 


2 


3 


Existing Geographic Coverage 


2 





2 


2 


2 

















1 





Cost of Ownership 


2 


1 


3 


3 


3 


1 


1 


1 


1 


1 


2 


1 


Sum of points: 


21 


19 


22 


24 


25 


22 


10 


17 


22 


21 


22 


22 


Max. No. of Points 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


Normalized Score: 


70% 


63% 


73% 


80% 


83% 


73% 


33% 


57% 


73% 


70% 


73% 


73% 



47 



Table 7.5 summarizes the results for architecture 4. Under the mesh 
architecture, wireless communications has a major advantage over wireline options 
due mainly to the high capital expenditure to implement a wireline technology in a 
mesh configuration. However, satellite and microwave technologies are expensive 
while Wi-Fi and WiMAX do not currently have the geographic coverage. Zigbee is 
eliminated due to its short distance reach. The result is cellular technology is the best 
option. Cellular networks cover the majority of United States residents with few 
exceptions in the rural areas or areas with challenging terrain. 

Table 7.5: Summary of Architecture 4 Metrics 



Criteria 


Architecture #4 (Mesh) 


Wireless 


Wireline 


"55 

00 

to 


CD 
> 

CO 

2 

o 

2 


C5 

£i 

to 

_3 

"cd 
O 


S" 

CO 
CO 

_3 

"CD 

O 


CD 

CO 

"cd 
O 


X 

< 


CD 
CO 

_o 

O) 
N 


Ll 


Q? 
H 

'CO 
Q. 

"D 
0) 

to 

1 


CD 
.O 
CO 

O 

X 

CO 

o 
O 


O 

_i 
Q. 


CD 
.Q 
CO 

O 

o 

o 

CD 
.Q 

Ll 


Bandwidth / Data Rate 


3 


3 


1 


2 


3 


3 


1 


3 


3 


3 


2 


3 


Latency 


1 


2 


2 


2 


1 


3 


1 


3 


3 


3 


3 


3 


Security 


3 


3 


2 


2 


3 


3 


2 


2 


3 


2 


2 


3 


Scalability 


1 


1 


2 


3 


3 


3 


1 


1 


1 


1 


2 


1 


Reliability 


2 


2 


2 


2 


2 


2 


1 


2 


3 


3 


2 


3 


Interoperability 


2 


2 


2 


2 


2 


1 


1 


3 


3 


3 


2 


2 


Resilience 


2 


2 


3 


3 


3 


3 


2 


1 


3 


3 


3 


3 


Distance Reach 


3 


3 


3 


3 


3 


3 





1 


2 


2 


2 


3 


Existing Geographic Coverage 


2 





2 


2 


2 

















1 





Cost of Ownership 


2 


1 


3 


3 


2 


1 


1 


1 


1 


1 


2 


1 


Sum of points: 


21 


19 


22 


24 


24 


22 


10 


17 


22 


21 


21 


22 


Max. No. of Points 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


Normalized Score: 


70% 


63% 


73% 


80% 


80% 


73% 


33% 


57% 


73% 


70% 


70% 


73% 



48 



Table 7.6 summarizes the results for architecture 5, which is based on using 
existing Internet connections to the cloud. This architecture is unique because it 
leverages existing Internet service the majority of end users have, which makes it 
least expensive architecture to deploy. Hence, using the Internet for Smart Grid 
communications is almost free for those who already have an Internet service. Based 
on the overall criteria, Internet service over TWP, which is called Digital Subscriber 
Line (DSL), is the best option due to its widespread geographic coverage. 
Table 7.6: Summary of Architecture 5 Metrics 



Criteria 


Architecture #5 (Internet Cloud) 


Wireless 


Wireline 


"35 
CO 


cd 
> 

CO 

o 
o 


(3 

LO 

d 

"55 
o 


5 

CO 

CO 

"CD 
O 


5 

CO 

"CD 
O 


X 

< 

5 


CD 
CD 
-Q 

a> 
N 


Ll 


ST 

H 

CO 
Q. 

"D 
O 

To 

h- 


<D 

.a 

CO 

O 

To 

X 

CO 

o 
O 


O 

_i 

CL 


CD 
JD 
CO 

O 
o 
"S. 
O 

CD 

.a 
Ll 


Bandwidth / Data Rate 


3 


3 


1 


2 


3 


3 


1 


3 


3 


3 


2 


3 


Latency 


1 


2 


2 


2 


1 


3 


1 


3 


3 


3 


3 


3 


Security 


3 


3 


2 


2 


3 


3 


2 


2 


3 


2 


2 


3 


Scalability 


1 


1 


2 


3 


3 


3 


1 


1 


3 


2 


2 


1 


Reliability 


2 


2 


2 


2 


2 


2 


1 


2 


3 


3 


2 


3 


Interoperability 


2 


2 


2 


2 


2 


1 


1 


3 


3 


3 


2 


3 


Resilience 


2 


2 


3 


3 


3 


3 


2 


1 


3 


3 


3 


3 


Distance Reach 


3 


3 


3 


3 


3 


3 





1 


2 


2 


2 


3 


Existing Geographic Coverage 


2 





1 


2 


2 











2 


1 


1 





Cost of Ownership 


1 


1 


2 


2 


1 


1 


1 


1 


3 


3 


2 


1 


Sum of points: 


20 


19 


20 


23 


23 


22 


10 


17 


28 


25 


21 


23 


Max. No. of Points 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


30 


Normalized Score: 


67% 


63% 


67% 


77% 


77% 


73% 


33% 


57% 


93% 


83% 


70% 


77% 



49 



Since a specific technology and architecture combination may not be 
available nationwide, it is important to provide few choices that can work in different 
environments. Table 7.6 presents the top five scoring scenarios out of all possible 
combinations i.e., scenarios presented in tables 7.2 - 7.6. It is clear that architecture 
5, Internet Cloud, has the highest score for the overall metrics. Additionally, Internet 
service over TWP and Coax cable are best media/technology options, due to existing 
widespread coverage and relatively low monthly costs. 

Table 7.7: Top Five Architecture and Technology Combinations 



Criteria 


Architecture #3 
Architecture #1 Architecture #2 .. . . . Architecture #5 

(Interconnected 
(Direct Connect) (Aggregator) (Internet Cloud) 


Wireless Wireless Wireless 


Wireline 


& 

CO 
"CD 

o 


(3 

CO 

"CD 
O 


(3 
;?. 

CO 

"o 
O 


ST 

CO 

o_ 

O 

to 

s 

h- 


CD 
.Q 
CO 

O 
"co 

X 

8 
o 
O 


Bandwidth / Data Rate 


3 


3 


3 


3 


3 


Latency 


1 


1 


1 


3 


3 


Security 


3 


3 


3 


3 


2 


Scalability 


3 


3 


3 


3 


2 


Reliability 


2 


2 


2 


3 


3 


Interoperability 


2 


2 


2 


3 


3 


Resilience 


3 


3 


3 


3 


3 


Distance Reach 


3 


3 


3 


2 


2 


Existing Geographic Coverage 


2 


2 


2 


2 


1 


Cost of Ownership 


3 


3 


3 


3 


3 


Sum of points: 


25 


25 


25 


28 


25 


Max. No. of Points 


30 


30 


30 


30 


30 


Normalized Score: 


83% 


83% 


83% 


93% 


83% 



50 



7.4 Conclusion 

After analyzing the five architectures and applicable wireline and wireless 
technologies for deployment in the Distribution Network in support of Smart 
Grid objectives, it is evident that each architecture and technology combination 
has strengths and weaknesses. Additionally, a single architecture solution will 
not be suitable for every deployment and in any environment. Hence, the author 
provides the top five scoring architectures and technology combinations. 
Architecture 5 is the overall favorable choice. This architecture functions with 
both wireline and wireless technologies, provides most flexibility, least cost of 
ownership, has widespread coverage and scales to support large deployments. 
Two concerns about this architecture include security risks from using the 
Internet to transport sensitive data and the utilities' acceptance to use third party 
providers for the communication networks. The first concern is manageable with 
added security layers. Currently, the Internet is widely accepted for sensitive 
financial transactions including online shopping, banking and stocks transactions. 
As for the second concern, while most utilities prefer to have complete 
ownership and total control of the communication networks that support Smart 
Grid, deployment costs and implementation timelines will force utilities to 
revaluate their position and start partnering with communication providers to 
realize Smart Grid benefits sooner than later. 



51 



Future study opportunity is to evaluate a mixture of technologies to 
implement each of the five architectures. For example, use PLC and cellular to 
build mesh architecture. Such approach will leverage vast power lines for 
primary link and use cellular links to complete the mesh network. 



52 



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57